EFFECT OF HYDROCARBON AND AMINE DILUENTS ON THE PROPERTIES OF DICUMYLPEROXIDE CURED STYRENE-BUTADIENE RUBBER .1. GUM COMPOSITIONS

Gum SBR compositions containing dicumyl peroxide and either alkane (no nadecane) or amine (octadecylamine or oleylamine) diluent were prepare d. Dilution caused a reduction in rheometer torque upon curing and in the resulting crosslink density based on solvent swelling. Results for each diluent were indistinguishable. However, tensile strengths and e specially storage moduli were different for nonadecane- and octadecyla mine-diluted vulcanizates. Added octadecylamine mildly reinforced the gum, while nonadecane lowered strength and stiffness. Furthermore, qui te strikingly, octadecylamine-diluted samples had a large, low-strain storage modulus, which decreased markedly with strain amplitude (Payne effect), while vulcanizates diluted with nonadecane showed no Payne e ffect.